Abstract: Based on the influence coefficient and virtual work principles, by adding a nominal mechanism to the snake-like robot body, a novel method of dynamic modeling for snake-like robots is presented. And the second order nonholonomic constraint equation of snake-like robots is also established under considering side slides of the condyles. With the expressions given, researches can directly develop imitation programs of the forward and inverse dynamics without complicated derivative or eliminating operations. An effective method is given for analyzing the characteristics of dynamic coupling of snake-like robots and developing the motion controller for snake-like ro-bots with the second order nonholonomic constraints equations. The method is not only available for the planar motion of snake-like robots, but also can be extended to analyze the dy-namic modeling and imitation of snake-like robots with spatial mechanism joints.

Key words: Dynamics, Influence coefficient, Nominal mechanism, Snake-like robot